1. Technical Field
The present invention relates to a method of estimating a degree of contamination of a front screen of an optical detection apparatus which includes the transmission of a plurality of transmission radiation pulses into a detection zone as well as the generation of a reception signal for each transmission radiation pulse, wherein the reception signal has a plurality of sampled values and a sampled value respectively indicates the intensity of the received back radiation of the respective transmission radiation pulse at a point in time at a predefined time interval from the transmission of the transmission radiation pulse. The invention additionally relates to a corresponding optical detection apparatus.
2. Related Art
An optical detection apparatus, e.g. a laser scanner, usually has a front screen which is arranged in the beam path between a transmission unit of the optical detection unit and the environment to be detected.
EP 2 182 378 A1 discloses a laser scanner which performs a method for estimating a degree of contamination of a front screen. To evaluate the transmissibility of the front screen of the optical detection apparatus, the laser scanner is designed to compare a selected peak of a received reception signal with an expected signal shape.
Due to noise effects and further interference effects present in the reception signal, an existing contamination of the front screen can in this respect only be detected with a limited reliability and the degree of contamination of the front screen can only be determined with limited accuracy.
In another method for estimating a degree of cleanliness of a front screen, additional LEDs are used which transmit light which irradiates the front screen and is detected by a photodiode. A contamination of the front screen can in this respect be detected by monitoring the photodiode current. The front screen is in this respect positioned obliquely with respect to a direction of transmission of the scanner so that the light of the LED irradiates the front screen and can be detected by the photodiode arranged beneath the LED in a housing of the scanner. This results in a front screen in the form of a frustoconical jacket, with this form producing an additional space requirement.